Larry Lyons: Those magical pine conesPublished 10:38am Thursday, October 22, 2009
After more than ten years of columns coming up with new ideas is getting pretty challenging. She noticed a big, cone laden fir tree and started asking questions about pine cones. Why do they only grow in the upper branches? How long does it take for the seeds to mature and so on? Bingo, she once again saved me for another week.
Pine cones are nothing short of magical. The familiar woody cones we sling about with the lawnmower are the female cones that produce seeds. There are also pollen producing male cones but these are actually modified leaves. They’re much smaller, not woody like we think of pine cones and die and disappear at the end of the growing season. Most of this discussion will be about the female cones. All conifer trees have cones. Many species have the typical cone shaped cones but other’s cones vary from round to cylindrical to egg shaped. Some even look like berries. Sizes vary hugely between species from less than an inch long to nearly two feet in length.
In the pine family (pines, spruces, firs, cedars and larches) the cone’s scales overlap each other like fish scales. There are actually two types of scales. Small, leaf-like bract scales form first. Underneath each bract scale a much larger, woody seed scale forms. At the base of each seed scale are two ovules which turn into seeds after they are fertilized with pollen. At just the right time when tiny pollen particles from the male cones drift on the breezes the female cone’s scales open temporarily to receive the pollen.
After the ovules are fertilized the scales close and protect the seeds with armor plating while they mature. But then there are the weird ducks of the family. Some species like juniper and yew produce what appears to be a berry. Though berry-like in appearance it is actually a fleshy cone. The yew’s brightly colored, sweet, berry-like cone is a single scale with one, deadly poisonous seed. Birds readily eat the berries but pass the seeds through their system undamaged, avoiding a fatal poisoning.
With most conifers the seeds mature in about six to eight months however cedars take 12 months and the true pines one and half to two years. When the seeds are ready the cone again opens, releasing the seed. In most species the cone opens by the scales drying out and flexing back. When the humidity is low the cone opens, when the weather is damp it closes. This opening and closing with the weather continues even after the seeds are released and the cone falls to the ground. Savvy firefighters judge the dryness of the forest floor by the pine cones. If they’re open get your gear ready. If closed it’s too damp for fire, go have a beer. Releasing seeds only in dry weather assures the tiny, wind blown seeds are carried as far away from the mother tree as possible. With some species such as the firs, cedars and larches the cone actually disintegrates.
In certain fire dependant conifers such as jack pine and redwoods the bract and seed scales are fused together and need the intense heat of fire to make the cone open and release the seeds. That’s why California’s redwood forests are in trouble. All fire is suppressed and there is no reproduction happening.
Most conifers grow male and female cones on the same tree. The large female cones are near the top of the tree while the inconspicuous male cones are lower. It is theorized that this reduces the likelihood of a tree being fertilized by its own pollen. It’s unlikely the pollen from the male cone will blow straight up. It usually blows outward and then gradually drifts up on the breezes to the tops of neighboring trees. In most species (but not all) the female cones are located at the tips of branches while the male cones are near the base of the branch.
Carpe diem, and any topic suggestions would be welcomed.
Larry Lyons writes a weekly outdoor column for Leader Publications. He can be reached at firstname.lastname@example.org